Drill bit



W. P. M KAIN Nov. 8, 1966 DRILL BIT Original Filed June 14, 1962 INVENTOR Walter P. Mc Kain United States Patent 3,283,837 DRILL BIT Walter P. McKain, Parkersburg, W. Va., assignor to Acme Fishing Tool Company, Parkersburg, W. Va., a corporation of West Virginia Continuation of application Ser. No. 202,607, June 14, 1962. This application Feb. 1, 1965, Ser. No. 429,534 1 Claim. (Cl. 175-414) This application is a continuation of my copending application Serial No. 202,607, filed June 14, 1962, since abandoned.

This invention relates to a drill .bit and particularly to a drill 'bit for use in cable tool percussion type drilling. My drill bit is constructed in a novel way so that it penetrates all types of earth formations, ranging from hard rock to soft clay, faster and more efficiently than any other cable tool percussion bit previously available. It operates at high efficiency for an unprecedented operating period despite substantially wearing away of the cutting teeth and reduction by wear of the outside diameter.

It is well known to those skilled in the art of cable tool drilling that various types of earth formations are encountered in drilling a well. Earth formations may vary in the same well, from soft earth overburden, which is not self-supporting and requires pipe or casing to constitute the wall of the well, to the hardest granite, which is self-supporting and itself constitutes the wall of the well. The well may pass through strata of gravel, quicksand, slate, shale, clay, boulders, fissures, faults, tilted or sloping formations and caves. Penetrating such different formations with optimum effect usually requires varying techniques as Well as different shaped bits.

In the cable tool method of drilling the drill bit may be attached by a threaded connection to a heavy bar or drill stem, which is suspended from the drilling machine by a cable. The drilling machine causes the cable to cyclically raise the drill bit in the hole and allow it to fall under the influence of gravity. The number of cycles per minute depends on the length of stroke, weight of the drill bit and associated tools, depth of the hole and other factors. The number of cycles per minute usually varies between twenty-five and sixty-five. The upper end of the drilling cable is wound on a drum called a bull reel controlled by a brake. Feeding of the cable as the hole deepens is accomplished by releasing the bull reel brake and permitting the bull reel to rotate slightly. There is usually some tension exerted on the cable as the bit strikes bottom. The amount of such tension is determined by the judgment of the driller through control of the adjustment of the bull reel brake.

When drilling 'hard rock it is desirable that there be little tension in the cable at the moment of impact so that the falling bit delivers the maximum energy for crushing the rock. The converse is true when drilling soft formations, where little energy is required for crushing, and the rate of penetration must be retarded by increasing the tension in the drilling cable at the moment of impact. It is always necessary to have a certain amount of water in the hole when drilling in either hard or soft formations to hold the cuttings in suspension so they may be removed periodically by bailing. The rate of penetration in hard rock depends largely on the rate at which the bottom of the hole can be crushed or comrninuted; in hard rock drilling suspension of the cuttings is usually a minor problem. But the penetration of soft formations can only proceed as rapidly as the cuttings are placed in suspension. This is called mud mixing. A drill bit most suitable for drilling hard rock is usually a p we very poor mud mixer. This is particularly true of multiwing, X-pattern and ordinary chisel point bits.

Drillers generally are loath to stop drilling and change bits to suit earth conditions resulting in sacrifice of optimum penetration in both hard and soft formations by using the same type of bit to drill from top to bottom. An ordinary chisel point bit is most commonly used. The reluctance of drillers to change the type of bit to suit the variable kinds of formation explains in large measure the persistent failure of the cable tool driller to accept bit designs more eflicient for drilling hard rock. Little or no thought has been given to the design of a bit to efficiently drill soft formations. To the best of my knowledge no one prior to my invention developed a cable tool bit which will drill both hard and soft formations with optimum efliciency.

The bit of my invention has been used successfully in drilling all types of hard and soft formations. with penetration rates up to more than 100% greater than those obtainable using conventional bits. It drills a straight hole through boulders, caves, crevices and broken and sloping formations where conventional bits would lead off or cease to drill altogether. To the best of my knowledge no other bit has accomplished such results.

In the design of my drill bit I desirably employ a new principle which results in unprecedented increase in drill bit life without resharpening. Instead of making the cutting teeth sharp in the direction of drilling l[ preferably .form the cutting faces of the cutting teeth as fiat surfaces disposed substantially in a plane normal to the length of the drilling bit and shape the teeth so that each tooth for a substantial distance from the cutting face toward the base of the tooth is defined at the sides by substantially parallel faces so that the area of the flat surface constituting the cutting face of the tooth remains substantially constant despite substantial wearing away of the tooth at the cutting face thereof.

The provision of teeth as above described has advantages which appear not to have been perceived heretofore by those skilled in the art. cutting teeth permit the use of very high pressures in drilling and the crushing of a much larger area of rock than can be crushed with a chisel point cutter. In using a chisel point cutter, which has a cutting edge which is substantially a line as distinguished from an area, the unit pressure is so great that while the rock is easily cut at the line of contact the cutting edge of the cutter becomes quickly dulled so that it will no longer penetrate the rock and the bit has to be removed from service and sharpened. With my drill bit the rock is effectively crushed over a substantial area.

The cutters are desirably so spaced that when the optirnum load is applied the entire area between the cutters is fractured. This occurs when the rock directly under the flat-bottom cutters fails in compression; it is pulverized and caused to exert substantially fluid pressure laterally against the rock on each side, which causes such rock to fail in shear. Chisel point cutters cannot perform in this manner. Tests of my bit on down-hole air drills produced granite chips as large as wide. Due to this wide fracture effect two blows of my bit occurring at rotation will effectively fracture the entire surface of the bottom of the hole. Also in using my drill bit there no rapid dulling of a cutting edge as with a chisel point cutter. Thus the drilling efiiciency of my bit is superior from the start of drilling; and as my bit wears down, due to the fact that the teeth for a substantial distance from the cutting face toward the base are defined at the sides by parallel plane faces, the teeth remain of uniform crushing capacity and can be used for long periods of time 'without resharpening. 1

The fiat faces of the My drill bit has longitudinally extending channels at opposite sides, such channels per se being conventional. It has a plurality of substantially parallel cutting teeth facing endwise of the drill bit. The cutting extremities of the teeth are disposed substantially in a plane normal to the length of the drill bit. Preferably, as above indicated, each of the cutting teeth has a base and terminates in a flat cutting face and for a substantial distance from the cutting face toward the base thereof is defined at its sides by substantially parallel faces so that the area of each of the flat cutting faces of the teeth remains substantially constant despite substantial wearing away of the teeth at the cutting faces thereof.

The teeth of my drill bit include a central tooth which preferably extends uninterruptedly diametrically completely across the head and at each Side of the central tooth shorter teeth in longitudinal alignment with each other whose outer ends terminate in the periphery of the drill bit spaced from the central tooth to form transverse channels and with their adjacent ends spaced apart to provide for communication between the longitudinal channel at that side and the transverse channels between the central tooth and the shorter teeth. The bottoms of the transverse channels preferably all lie substantially in a plane perpendicular to the length of the drill bit.

When the teeth are formed with their sides defined by substantially parallel faces as above described the width of the transverse channels remains substantially constant despite substantial wearing away of the teeth. The transverse channels extend to the periphery of the bit and hence into close proximity with the wall of the hole being drilled.

The bottoms of the transverse channels where they intersect the periphery of the drill bit form reaming edges. The reaming edges at their mid points are substantially normal to the length of the drill bit and for some distance to each side of their mid points they do not depart greatly from being normal to the length of the drill bit. This provides for exceptional reaming efliciency.

When drilling hard rock the transverse channels in the drill bit provide for optimum circulation of the drilling fluid, removing the cuttings from the bottom of the hole and keeping them in suspension, which speeds penetration. When drilling softer formations the transverse channels materially improve the mud mixing eflficiency of the drill bit. The teeth of the drill bit easily penetrate the soft material and force it up into the transverse channels whence it is extruded into the vertical channels of the drill bit. This action results in optimum diffusion of the solids into a state of suspension, further contributing to a higher rate of penetration.

'Ihe reaming edges of my drill bit provide, as above indicated, for exceptional reaming capacity. This is especially important in cable tool well drilling bits when the driller doesnt know where he is going to finish until he strikes production. It is important that he keeps the hole reamed out to the starting size so that each fresh bit can be run to bottom without wedging in an undersized hole. A drill bit without adequate reaming edges will wear tapered, stick in the hole and cease to penetrate. The reaming edges of my bit are located close to the bottom of the hole minimizing wearing of the bit to tapered shape.

Preferably the bottom of each of the longitudinal channels intersects the adjacent transverse channels substantially at the bottom thereof, insuring free communication and flow of drilling fluid between the channels in the face of the bit and the longitudinal channels. This is especially important in drilling in soft formations.

The features of my drill bit to which reference has been made above impart to the drill bit exceptional operating characteristics and efliciency for all around drilling regardless of the type of formation encountered.

Other details, objects and advantages of the invention will become apparent as the following description of a present preferred embodiment thereof proceeds.

In the accompanying drawings I have shown a present preferred embodiment of the invention in which FIGURE 1 is a side view of a drill bit embodying my invention viewed in a direction parallel to the cutting teeth;

FIGURE 2 is a side view of the drill bit shown in FIG- URE 1 viewed in a direction normal to the cutting teeth;

FIGURE 3 is an end view of the drill bit shown in FIG- URES 1 and 2 as viewed from the right-hand end of those figures;

FIGURE 4 is a cross-sectional view taken on the line IV-IV of FIGURE 2; and

FIGURE 5 is an enlarged fragmentary isometric view of the head and a portion of the shank of the drill bit.

Referring now more particularly to the drawings, I have chosen to illustrate my invention as embodied in a drill bit primarily adapted for use by the cable tool method of percussion drilling although it is to be understood that my invention is equally applicable to drill bits designed for other types of percussion drilling, such, for example, as drilling with the use of a down-the-hole air hammer.

As shown in FIGURES 1 and 2 my drill bit has a conventional tapered threaded end 2 for connection with a cable or other operating means. The drill bit comprises a shank 3 with a head 4 at the operative end of the shank. The drill bit is shown as having the conventional opposed longitudinal channels 5 for the pas-- sage of drilling fluid. The drill bit may have internal passage means (not shown) for conveying drilling fluid downwardly to the working area, the drilling fluid with entrained broken up rock and dirt passing upwardly through the channels 5. The drill bit as thus far described may be conventional.

I provide the drill bit With cutting teeth of novel form having the advantages above explained. In the structure shown in the drawings I provide on the head 4 and facing endwise of the drill bit a tooth 6 which is preferably substantially straight as shown which extends continuously completely across the head 4 at a portion of the head remote from the channels 5 and shorter teeth 7 at each side of the head, the teeth 7 at each side being in alignment with each other at opposite sides of the channel 5 at that side. The arrangement of the teeth is clearly shown in FIGURES 1, 3 and 5. All of the teeth 6 and 7 are preferably elongated and straight and parallel to one another. Each of the teeth has a base 8 on the head 4 and terminates in a cutting face 9 consisting of a flat surface disposed substantially in a plane normal to the length of the drill bit. Each of the teeth 6 and 7 for a substantial distance from the cutting face 9 thereof toward the base 8 thereof is preferably of substantially uniform cross-sectional area so that the area of the flat surface constituting the cutting face 9 remains substantially constant despite substantial wearing away of the tooth at the cutting face thereof. For optimum efiiciency the cutting faces of all of the teeth should be disposed substantially in a common plane normal to the length of the drill bit as shown in FIG- URES 1 and 2.

The side faces of each of the teeth 6 and 7 for a substantial distance from the cutting face toward the base thereof are shown as being planar and parallel. The planar and parallel portions of the side faces of each tooth preferably extend in the direction of the depth of the tooth a distance at least substantially equal to the width of the flat surface 9 constituting the cutting face of the tooth. Thus each tooth for a distance from the cutting face toward the base thereof at least substantially equal to the width of the flat surface constituting the cutting face of the tooth is preferably of substantially uniform cross-sectional area so that the area of the flat surface constituting the cutting face remains substantially constant despite wearing away of the tooth at the cutting face thereof for a distance substantially equal to the width of the cutting face.

In a preferred form of drill bit each cutting tooth terminates in a cutting face consisting of a flat surface at least about /4 inch wide disposed substantially in a plane normal to the length of the drill bit and the tooth for a distance of at least about A: inch from the cutting face toward the base is of substantially uniform crosssectional area so that the area of the flat surface constituting the cutting face remains substantially constant despite wearing away of the tooth at the cutting face thereof for a distance of at least about A inch. These dimensions and proportions are found to be optimum for most types of rock drilling; the bit wears undersize on the diameter and has to be resharpened long before the teeth wear down beyond the point at which they cease to be of uniform cross-sectional area.

The transverse channels above described are designated by reference numeral in the drawings and the reaming edges of the bit are designated by reference numeral 11. FIGURES 3 and 5 show the provision for free flow between the transverse channels 10 and the longitudinal channels 5 which is largely contributed to by the fact that the bottom of each of the longitudinal channels 5 intersects the adjacent transverse channels 10 substantially at the bottom thereof as shown at 12 in FIGURE 3.

While I have shown and described a present preferred embodiment of the invention it is to be distinctly understood that the invention is not limited thereto but may be otherwise variously embodied within the scope of the following claim.

I claim:

A drill bit having channels at opposite sides extending longitudinally of the drill bit and having a plurality of substantially parallel cutting teeth facing endwise of the drill bit, each of the cutting teeth having a base and terminating in a flat cutting face, the cutting faces of the teeth being disposed in a plane normal to the length of the drill hit, each of the teeth for a substantial distance from the cutting face toward the base there of being defined at its sides by parallel faces so that the area of each of the flat cutting faces of the teeth remains constant despite substantial wearing away of the teeth at the cutting faces thereof, the teeth including a central tooth extending uninterruptedly diametrically completely across the bit and at each side of the central tooth shorter teeth in longitudinal alignment with each other Whose outer ends terminate in the periphery of the drill bit spaced from the central tooth to form transverse channels and with their adjacent ends spaced apart to provide for communication between the longitudinal channel at that side and the transverse channels between the central tooth and the shorter teeth, the bottoms of the transverse channels being substantially flat and all lying in a plane perpendicular to the length of the drill bit, the width of the transverse channels remaining constant despite substantial wearing away of the teeth, the bottoms of the transverse channels intersecting the periphery of the drill bit to form reaming edges which at their mid points are substantially normal to the length of the drill bit.

References Cited by the Examiner UNITED STATES PATENTS 981,510 1/1911 Wilson 414 1,036,673 8/ 1912 Meguire 175-420 2,863,639 12/1958 Bredesen 175414 ERNEST R. PURSER, Primary Examiner.

CHARLES E. OCONNELL, Examiner.

N. C. BYERS, Assistant Examiner. 

